This invention relates to a solar heating system employing a liquid heat exchange medium such as water.
Significant technological progress has been made in solar heating systems in recent years, following the realization of limits on fossil fuels and the rapidly increasing cost thereof. Solar heating is becoming a practical reality in some geographical areas, particularly in the southern and southwestern parts of the united States, sometimes designated the sun belt. In the more nothern regions, as in the northwestern, midwestern, and northeastern parts of the United States however, where the number of sunny days is less, i.e. solar radiation is only intermittent and/or has less intensity, there is difficulty justifying the installation cost of solar equipment because of the considerably lower efficiency thereof. There are many cloudy or partly cloudy days when the collector cannot generate sufficient heat to raise the temperature in the storage system more than a few degrees above that of the space to be heated. Consequently, even though a substantial amount of total heat is theoretically available in the typical storage reservoir of several thousand gallons of liquid, there simply is not enough "driving potential" in terms of temperature differential between the heat storage liquid and the environmental space to be heated to enable effective heat transfer therebetween. The theoretical heat therefore cannot be effectively utilized. Hence, the solar system is typically deactivated at such times, with the heat required being totally generated by fossil fuel combustion. Unfortunately, the same geographic regions of cooler climate and less sunshine are more in need of whatever solar energy there is available.